The control mechanism disclosed in U.S. Pat. No. 4,541,497 to C. W. Riediger, et al on Sept. 17, 1985, and which was specifically constructed for steering and operating the transmission of a track-type vehicle, has been extremely well received by the industry. In such mechanism, a tiller arm extends outwardly from an upstanding member which is rotatable about a fixed axis, and the vehicle is steered as the tiller arm is swung in either direction away from a generally centered neutral position. In order to change at least one of the speed range of the vehicle and the direction of longitudinal movement of the vehicle, a handgrip portion is supported on the tiller arm for rotation about its own axis. Thus, the handgrip portion can be conveniently grasped by an operator's downwardly facing left-hand palm and as the vehicle is traveling forwardly it can be steered to the left by swinging the tiller arm forwardly. Simultaneously, the vehicle can be shifted from a forward to a reverse speed by merely twisting the handgrip portion about its own axis through a relatively limited angular range.
A mechanically separated speed selector lever has heretofore been used with the aforementioned steerable tiller arm and its twistable handgrip portion. This requires the operator to release the tiller arm and grasp the juxtaposed speed selector lever in order to make a speed range shift of the vehicle transmission. Upon completing the range shift, the speed selector lever is released and the left hand returned to the tiller arm. This is not only fatiguing and vexatious, but can delay the operator's attention from other tasks. Normally, the operator's right hand is used extensively for manipulating an implement control lever, and as the operator's left hand passes between the separated control members, there is a slight delay in using the right hand.
In addition, the separated speed selector lever has heretofore been automatically forced back to a neutral position when a separate parking brake handle has been applied. Consequently, when the parking brake is released it is positively assured that the vehicle is in neutral and not in an operating gear. Although the parking brake handle was inconvenient to reach and a relatively complex mechanical connection was used between these control members, it is a desirable feature.
While the control mechanism of aforementioned U.S. Pat. No. 4,541,497 is rugged and reliable, it is relatively complex and costly in construction because of the physically separated operating members and the multiplicity of links and levers associated between each one and the associated selector spools operated thereby.
Thus, what is desired is a simplified and reliable control mechanism for operating a vehicle that includes a swingable tiller arm for steering purposes, as well as integrated actuating members for separately controlling the direction of longitudinal movement of the vehicle and the speed range of the vehicle. The tiller arm and associated actuating members should be so constructed and arranged as to fully take into account the principles of economy of motion of a single hand. Preferably, the improved control mechanism should also include a fully integrated brake actuating member for engaging a parking brake and simultaneously assuring neutralization of the transmission associated with movement of the vehicle.
The present invention is directed to one or more of the problems as set forth above.